(1) Field of the Invention
The present invention relates to a process and compositions including a finely divided metal, metal oxide coated metal, metal oxide and other oxidized metal produced by the use of alkalides and electrides to reduce a soluble metal salt in an organic solvent. In particular, the present invention relates to a process which produces the finely divided metal, metal oxide coated metal or metal oxide or other oxidized metal depending upon the oxidizability of a metal initially produced by the process.
(2) Prior Art
Homogeneous reduction of noble metal salts by mild reducing agents, even in aqueous solution is well known. Solid alkali metals and suspensions of alkali metals are also often used as reductants. The use of homogeneous strong reducing agents in aprotic solvents to produce finely divided metals has been limited to reduction by aromatic radical anions and/or aromatic dianions such as sodium naphthalenide (Rieke, R., Science 246, 1260-1264 (1989)). Often the reductions are slow and must be done at the reflux temperatures of THF. The most common source of solvated electrons is found in metal-ammonia and metal-amine solutions. Indeed, these solutions are commonly used in industry and research to reduce organic compounds (Birch reductions). The problem encountered with transition metal reductions by metal-ammonia solutions is the formation of metal amides and imides by deprotonation of the solvent. Complex mixtures result from such reactions and one seldom gets the transition metal itself.
Examples of metal particle production are:
1. Mild reduction of noble metals in the presence of soluble polymers to yield 10-50 .ANG. particles. H. Hirai, Y. Nakao and N. Toshima, J. Macromol. Sci-Chem., A12, 1117 (1978); A13, 727 (1979); H. Hirai, ibid, A13, 633 (1979).
2. Zero-valent compounds such as Fe(CO).sub.5 can be thermally decomposed in polymers to yield colloidal dispersions of metal. T. W. Smith and D. Wychick, J. Phys. Chem., 84, 1621 (1980).
3. Metal vapor deposition in a solvent matrix can give small metal particles, M. Kilner, N. Mason, D. B. Lambrick, P. D. Hooker and P. L. Timms, J. Chem. Soc. Chem. Comm., 356 (1987). K. Kimura and S. Bandow, Bull. Chem. Soc. Jpn, 56, 3578 (1983); K. Kimura, ibid, 57, 1683 (1984); 60 3093 (1987).
4. Heterogeneous reduction by alkali metals in ethers with or without an aromatic compound present as an electron carrier has been used to prepare metals. R. D. Rieke et al., J. Am. Chem. Soc., 96, 1775 (1974); J. Org. Chem., 40 2253 (1975); ibid 44, 3069 (1979); ibid, 46, 4323 (1981) .
Research with alkalides and electrides as described in:
(1) U.S. Pat. No. 4,107,180 to Dye;
(2) J. Am. Chem. Soc. 96, 608-609 (1974);
(3) J. Physical Chem. 79, 3065-3070 (1975);
(4) Angew. Chem. Int. Ed. Engl. 18, 587-598 (1979);
(5) Alkali Metals McGraw-Hill Yearbook of Science and Technology 87-89 (1981);
(6) Inorganic Chem., 21, 1966-1970 (1982);
(7) J. Am. Chem. Soc. 105, 6490-6491 (1983);
(8) Chemistry in Britain 20 210-215 (1984);
(9) Progress in Inorganic Chemistry, John Wiley & Sons 32, 327-441 (1984);
(10) J. Physical Chem. 88, 3852-3855 (1984);
(11) J. Am. Chem. Soc. 108, 3534-3535 (1986);
(12) J. Am. Chem. Soc. 109, 5561-5563 (1987);
(13) J. Am. Chem. Soc. 101, 7203-7204 (1987);
(14) Valency and Charge Distribution, In Alkalide and Electride Salts, Proceedings of The Robert A. Welch Foundation Conference on Chemical Research XXXII Valency, pg 65-91 (1988);
(15) Nature 331, 599-601 (1988);
(16) J. Coord Chem. 18, 121-128 (1988);
(17) J. Am. Chem. Soc. 111, 935-938 (1989);
(18) J. Am. Chem. Soc. 111, 5957-5958 (1989);
(19) Pure & Appl. Chem. 61, 1555-1562 (1989); and
Ann. Rev. Phys. Chem. 38, 271-301 (1987); showed that relatively concentrated solutions (&gt;0.1 M in many cases) are obtained which contain e.sub.s and/or M.sup.- in aprotic solvents such as dimethyl ether. This research provided the possibility to carry out reductions in the absence of proton sources other than the highly non-acidic --CH.sub.2 -- and --CH.sub.3 protons of the solvent and complexant; however, the means for accomplishing such a reaction was not known.